Putting Microbes to Work on Subsurface Contamination

Victor M. Ibeanusi

doi:10.4172/2155-6199.1000e111

ISSN: 2155-6199

Journal of Bioremediation & Biodegradation

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Putting Microbes to Work on Subsurface Contamination

Victor M. Ibeanusi^*
Environmental Science and Studies Program, Spelman College, Atlanta GA 30314, USA
Corresponding Author :	Victor M. Ibeanusi Environmental Science and Studies Program Spelman College, Atlanta GA 30314, USA E-mail: vibeanus@spelman.edu
Received April 24, 2012; Accepted April 26, 2012; Published April 28, 2012
Citation:Ibeanusi VM (2012) Putting Microbes to Work on Subsurface Contamination. J Bioremed Biodegrad 3:e111. doi: 10.4172/2155-6199.1000e111
Copyright: © 2012 Ibeanusi VM. This is an open-a ccess article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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Imagine the year in which world’s major environmental contaminants are a thing of the past. A year when new biotechnologies and a changed economic climate combined with enlightened government policies and a pronounced shift in societal and corporate attitudes have resulted in dramatic decreases in the volumes and toxicity of industrial wastes generated by each country’s industries. A year in which limited use of fossil fuel and crude oil spills, such as those that threatened the Gulf coast can be biodegraded within a reasonable period before they cause major environmental impacts. The latter is the focus of this editorial commentary.

Light Non Aqueous Phase Liquids (LNAPLs), which include petroleum products has historically been perceived as a significant environmental threat by the general public and the regulatory community. New assessments that provide the critical information necessary to evaluate and define clean-up goals for LNAPL are needed. A major obstacle is the recovery of the residual and free phase fractions that are trapped due to capillary and interfacial forces. This implies that conventional pump and treat methods will require excessive energy and costs to for extraction of excessive pore volumes of the groundwater to recover the trapped phases due to mass transfer limitations.

Treatment options such as those utilizing natural processes have been found to be efficient and cost-effective. For example, other wellknown natural processes such as in: nutrient cycling, flow of energy through the various trophic levels of the ecosystems, and natural attenuation of pollutants has served as the underlying template in the sustainability of the ecosystems around the world. By understanding and enhancing these important natural processes, the need for cost efficiency and sustainability has now emerged as the underlying factors for measuring remediation processes and assessment of environmental quality.

The inherent ability of microbes to biodegrade organic contaminants such as LNAPLs can be enhanced through processes that combine the use of surfactants, enhanced mobilization, biostimulation, mineralization and bioaugmentation indicating the growing importance for a better understanding and use of these emerging biotechnologies. For example, the combined use of surfactants can significantly enhance the rate of extraction of LNAPLs from groundwater due to increased solubility of the aqueous phase that result from the presence of surfactant micelles.

A number of limiting factors have been recognized to affect the biodegradation of LNAPLs, many of which have been extensively described in literatures. The composition and inherent biodegradability of the LNAPL hydrocarbon pollutant is the first and foremost important consideration when the suitability of a microbial-system approach is to be assessed.

Among physical factors, temperature plays an important role by directly affecting the chemistry of the pollutants as well as affecting the physiology and diversity of the microbial flora. There is abundant evidence that at low temperatures, the viscosity of the LNAPLs increased, while the volatility of the toxic low molecular weight hydrocarbons were reduced, delaying the onset of biodegradation. Temperature also affects the solubility of hydrocarbons. Although hydrocarbon biodegradation can occur over a wide range of temperatures, the rate of biodegradation generally decreases with the decreasing temperature. A consensus of opinions from literature show that highest degradation rates occur in the range 30-40 C in soil environments, 20-30C in some freshwater environments and 15-20C in marine environments.

Nutrients are keys to ensure a robust sustained microbial growth for successful biodegradation of LNAPL contaminants especially nitrogen, phosphorus, potassium (NPK), and in some cases iron. Some of these nutrients could become limiting factor thus affecting the biodegradation processes. The role of nutrients in biodegradation is closely tied to the soil type. The main factor in this is the bioavailability of the LNAPL. Natural soils consist of particles of different sizes, which imply that the pores in the soil matrix are of different sizes. Some of the pores in soil materials are smaller than the indigenous bacteria and therefore inaccessible for them. In the pores that are accessible for bacteria, bacterial growth can be limited by slow mass transfer of nutrients and organic substrate. This means that the organic content of a soil determines to a large extend how much of the LNAPL will be absorbed by the soil particles.

Soil moisture content also plays a critical role in microbial degradation of hydrocarbons. Due to the bacterial metabolism, which utilizes water, soil moisture content has a significant effect on biodegradation rates. The implication is that aerobic degradation may be most active in the capillary fringe of a soil, though it can be limited by several local conditions.

This editorial commentary gives you a sneak preview to the growing importance of microbes in LNAPLs degradation and other volatile organic compounds. I encourage you to look forward to my upcoming publication, tiled Putting Microbes to Work on Subsurface Contamination: A Focus on LNAPLS for in depth discussion of these biotechnologies.